And the risk factor needs to be compared to the risk factor of not taking it.
We actually do know, in general, what those risk factors are even if they cannot be nailed down to extremely specific numbers. One thing we can be pretty sure about, the risk factor of the vaccine will be less than the risk factor of COVID. Even with the relatively small number of deaths that occur from getting the infection, it is still a very high death rate particularly when compared to the risk factors of vaccines and even more so when considering that contracting COVID is so damn likely.
We really don't know because we haven't had enough years to know. The testing that takes place now is impossible to tell you what could happen to you ten years from now. You need to monitor the vaccine for another 10 years to find out.
Remember the silicone breast implants? They were successful for many years. Then women started experiencing problems much later on. Finally the company that produced them was sued out of business if I remember correctly. Now.......one might think they are safe because women have been getting them for five years. Others would ask themselves in spite of it's success rate, is it really smart to put a product in your body that an oil change place uses to keep your car doors from squeaking?
Anytime you put something new into your body, you have to be at least a little skeptical. Others will meet the challenge head on. The wife of a friend of mine volunteered to be a test subject for the vaccine. In some patients they used the actual vaccine. In others they used saline. She said she didn't feel any different or any side effects, so she believes she was injected with saline, but she still doesn't know. I told my friend his wife is a very brave person.